“The IssueWarningQuota parameter specifies the warning threshold for the size of the mailbox. If themailbox reaches or exceeds this size, the user receives a descriptive warning message.

In Office 365, the quota value is determined by the subscriptions and licenses that administrators purchase and assign in the Office 365 admin center. You can lower the quota value, but you can't exceedthe default value specified by the subscription or license.”

“The ProhibitSendQuota parameter specifies a size limit for the mailbox. If the mailbox reaches or exceeds this size, the mailbox can't send new messages, and the user receives a descriptive warning message.”

“The ProhibitSendReceiveQuota parameter specifies a size limit for the mailbox. If the mailbox reaches or exceeds this size, the mailbox can't send or receive new messages. Messages sent to the mailbox are returned to the sender with a descriptive error message. This value effectively determines the maximum size of the mailbox.”